U.S. patent application number 14/043676 was filed with the patent office on 2014-01-30 for medical sensor for reducing artifacts and technique for using the same.
This patent application is currently assigned to Covidien LP. Invention is credited to Clark R. Baker, Jr..
Application Number | 20140031653 14/043676 |
Document ID | / |
Family ID | 39152741 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140031653 |
Kind Code |
A1 |
Baker, Jr.; Clark R. |
January 30, 2014 |
MEDICAL SENSOR FOR REDUCING ARTIFACTS AND TECHNIQUE FOR USING THE
SAME
Abstract
A sensor may be adapted to reduce signal artifacts by deflecting
the effects of outside forces and sensor motion. A sensor is
provided with a rigid annular structure adapted to reduce the
effect of motion of a sensor emitter and/or detector. Further, a
method of deflecting or minimizing outside forces and sensor motion
is also provided.
Inventors: |
Baker, Jr.; Clark R.;
(Newman, CA) |
Assignee: |
Covidien LP
Mansfield
MA
|
Family ID: |
39152741 |
Appl. No.: |
14/043676 |
Filed: |
October 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13412421 |
Mar 5, 2012 |
8577436 |
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14043676 |
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|
11507814 |
Aug 22, 2006 |
8145288 |
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13412421 |
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Current U.S.
Class: |
600/340 ;
600/322; 600/344 |
Current CPC
Class: |
A61B 5/14552 20130101;
A61B 5/6838 20130101; A61B 5/6826 20130101 |
Class at
Publication: |
600/340 ;
600/344; 600/322 |
International
Class: |
A61B 5/1455 20060101
A61B005/1455; A61B 5/00 20060101 A61B005/00 |
Claims
1. A sensor comprising: a conformable bandage-type sensor body
configured to be directly applied to a patient's digit; an emitter
and a detector disposed on a tissue contacting surface of the
sensor body, wherein the emitter is configured to emit light into
the patient's tissue, and wherein the detector is configured to
receive the light to determine a physiological characteristic of
the patient; and a rigid structure not fixedly attached to the
sensor body and comprising protrusions configured to deflect
movement of the patient's digit away from the emitter and the
detector, wherein the protrusions are orthogonal to the patient's
digit when the rigid structure is coupled to the sensor body and
wherein the rigid structure covers the sensor body in an area
corresponding to the emitter and the detector and covers less than
50% of a surface area of the sensor body when the sensor is applied
to the patient.
2. The sensor of claim 1, wherein at least a portion of the rigid
structure applies a pressure on the emitter, the detector, or a
combination thereof.
3. The sensor of claim 1, wherein the rigid structure comprises an
arch.
4. The sensor of claim 3, wherein the protrusions extend outwardly
from terminating ends of the arch.
5. The sensor of claim 1, wherein the protrusions comprise a
damping component.
6. The sensor of claim 5, wherein the dampening component comprises
a spring.
7. The sensor of claim 1, wherein the sensor comprises at least one
of a pulse oximetry sensor or a sensor for measuring a water
fraction.
8. The sensor of claim 1, wherein the rigid structure applies
pressure that secures the sensor body onto the patient's digit.
9. The sensor of claim 1, wherein the protrusions are coupled to
the rigid structure at a location corresponding to a side of the
patient's digit when the rigid structure is applied to the
sensor.
10. A method comprising: applying a conformable bandage-type sensor
body to a patient's finger, the conformable sensor body comprising
an emitter and a detector disposed on a tissue-contacting surface
of the sensor body, wherein the emitter is configured to emit light
into the patient's finger; and applying a rigid annular structure
over the sensor body such that the rigid annular structure contacts
the sensor body only at locations corresponding to sides of the
patient's finger and wherein the rigid annular structure has a
largest gap with the sensor body in an area corresponding to the
emitter and the detector.
11. The method of claim 10, wherein the sensor comprises at least
one of a pulse oximetry sensor or a sensor for measuring a water
fraction.
12. The method of claim 10, wherein the rigid annular structure
secures the sensor body on the patient's finger.
13. The method of claim 10, wherein at least one of the emitter or
the detector is positioned on a top of the patient's finger when
the sensor body is applied.
14. The method claim 10, wherein the rigid annular structure
comprises a substantially oval shape.
15. The method of claim 10, wherein the tissue-contacting surface
of the sensor body comprises an adhesive layer.
16. A physiological monitoring system comprising: a sensor
comprising: a conformable bandage-type sensor body configured to be
directly applied to a patient's digit; an emitter and a detector
disposed on a tissue contacting surface of the sensor body, wherein
the emitter is configured to emit light into the patient's tissue,
and wherein the detector is configured to receive a signal in
response to the emitted light, wherein the signal is representative
of a physiological parameter; and a removable rigid structure
disposed over the sensor body comprising protrusions configured to
deflect movement of the patient's digit away from the emitter and
the detector, wherein the protrusions extend away from the
patient's tissue when the rigid structure is coupled to the sensor
body and wherein the rigid structure covers the sensor body in an
area corresponding to the emitter and the detector and covers less
than 50% of a surface area of the sensor body when the sensor is
applied to the patient; and a monitor coupled to the sensor and
configured to receive the signal from the detector to determine the
physiological parameter.
17. The physiological monitoring system of claim 16, wherein the
removable rigid structure is an arch.
18. The physiological monitoring system of claim 17, wherein the
protrusions extend outwardly from terminating ends of the arch.
19. The physiological monitoring system of claim 16, wherein the
removable rigid structure applies a pressure to the sensor body to
retain the sensor body in place on the patient's digit.
20. The physiological monitoring system of claim 19, wherein the
sensor comprises a pulse oximetry sensor or a sensor for measuring
water fraction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. patent application Ser. No. 13/412,421, filed on Mar. 5, 2012,
and U.S. Pat. No. 8,145,288, filed on Aug. 22, 2006, which are
incorporated herein by reference in their entirety for all
purposes.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to medical devices
and, more particularly, to sensors used for sensing physiological
parameters of a patient.
[0004] 2. Description of the Related Art
[0005] This section is intended to introduce the reader to various
aspects of art that may be related to various aspects of the
present invention, which are described and/or claimed below. This
discussion is believed to be helpful in providing the reader with
background information to facilitate a better understanding of the
various aspects of the present invention. Accordingly, it should be
understood that these statements are to be read in this light, and
not as admissions of prior art.
[0006] In the field of medicine, doctors often desire to monitor
certain physiological characteristics of their patients.
Accordingly, a wide variety of devices have been developed for
monitoring many such characteristics of a patient. Such devices
provide doctors and other healthcare personnel with the information
they need to provide the best possible healthcare for their
patients. As a result, such monitoring devices have become an
indispensable part of modern medicine.
[0007] One technique for monitoring certain physiological
characteristics of a patient is commonly referred to as pulse
oximetry, and the devices built based upon pulse oximetry
techniques are commonly referred to as pulse oximeters. Pulse
oximetry may be used to measure various blood flow characteristics,
such as the blood-oxygen saturation of hemoglobin in arterial
blood, the volume of individual blood pulsations supplying the
tissue, and/or the rate of blood pulsations corresponding to each
heartbeat of a patient. In fact, the "pulse" in pulse oximetry
refers to the time varying amount of arterial blood in the tissue
during each cardiac cycle.
[0008] Pulse oximeters typically utilize a non-invasive sensor that
transmits electromagnetic radiation, such as light, through a
patient's tissue and that photoelectrically detects the absorption
and scattering of the transmitted light in such tissue. One or more
of the above physiological characteristics may then be calculated
based upon the amount of light absorbed and scattered. More
specifically, the light passed through the tissue is typically
selected to be of one or more wavelengths that may be absorbed and
scattered by the blood in an amount correlative to the amount of
the blood constituent present in the tissue. The measured amount of
light absorbed and scattered may then be used to estimate the
amount of blood constituent in the tissue using various
algorithms.
[0009] Pulse oximetry readings measure the pulsatile changes in
amount and type of blood constituents in tissue. Other events
besides the pulsing of arterial blood may lead to modulation of the
light path, direction, and the amount of light detected by the
sensor, creating potential error in these measurements. Current
pulse oximetry techniques may be sensitive to movement, and various
types of motion may cause artifacts that may obscure the blood
constituent signal. In the emergency room, critical care, intensive
care, and trauma center settings, where pulse oximetry is commonly
used for patient monitoring, the wide variety of sources of signal
artifacts may include moving of a patient or the sensor by
healthcare workers, physical motion of an unanaesthetised or
ambulatory patient, shivering, seizures, agitation, response to
pain and loss of neural control. These motions can have similar
frequency content to the pulse, and may lead to similar or even
larger optical modulations than the pulse.
[0010] Two categories of pulse oximetry sensors in common use may
be classified by their pattern of use: the disposable sensor and
the reusable sensor. Disposable sensors are typically flexible
bandage-type structures that may be attached to the patient with
adhesive materials, providing a contact between the patient's skin
and the sensor components. Disposable sensors have multiple
advantages, including ease of conformation to the patient. The
flexible nature of disposable sensors further renders them
susceptible to signal artifacts caused by mechanical deformation of
the sensor, which changes the amount of light detected. Reusable
sensors, often semi-rigid or rigid clip-type devices, are also
vulnerable to signal artifacts, such as artifacts caused by partial
opening of the clip in response to patient motion. Both categories
of sensors may have modulations of detected light induced by the
physical motion of the sensor components with respect to each other
and the tissue.
[0011] Signal artifacts may sometimes be addressed by signal
processing and filtering to mitigate the effects of motion after
the motion has occurred. However, it would be desirable to provide
a sensor that reduces the occurrence of events that may lead to
signal artifacts.
SUMMARY
[0012] Certain aspects commensurate in scope with the originally
claimed invention are set forth below. It should be understood that
these aspects are presented merely to provide the reader with a
brief summary of certain forms that the invention might take and
that these aspects are not intended to limit the scope of the
invention. Indeed, the invention may encompass a variety of aspects
that may not be set forth below.
[0013] There is provided a sensor that includes: a sensor body; at
least one sensing element disposed on the sensor body; and at least
one rigid annular structure adapted to be removably applied to the
sensor body.
[0014] There is also provided a physiologic monitoring system that
includes: a pulse oximetry monitor; and a pulse oximetry sensor
adapted to be operatively coupled to the monitor. The sensor
includes: a sensor body; at least one sensing element disposed on
the sensor body; and at least one rigid annular structure adapted
to be removably applied to the sensor body.
[0015] There is also provided a method of operating a sensor that
includes: deflecting mechanical force with a rigid annular
structure dispersed around an emitter and a detector of a sensor
applied to a patient, wherein the rigid annular structure is
removably applied to the sensor.
[0016] There is also provided a method of manufacturing a sensor
that includes: providing sensor body; providing at least one
sensing element disposed on the sensor body; and providing at least
one rigid annular structure adapted to be removably applied to the
sensor body.
[0017] There is also provided a kit that includes: a sensor body;
an emitter and a detector disposed on the sensor body; and a
plurality of rigid annular structures of various sizes adapted to
be removably applied to the sensor body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Advantages of the invention may become apparent upon reading
the following detailed description and upon reference to the
drawings in which:
[0019] FIG. 1 illustrates a side view of an exemplary bandage-style
sensor with a removable ring structure applied to a patient's
finger;
[0020] FIG. 2 illustrates a side view of an exemplary bandage-style
sensor with a removable thimble structure applied to a patient's
finger;
[0021] FIG. 3 illustrates a side view of an exemplary bandage-style
sensor with a removable sleeve structure applied to a patient's
finger;
[0022] FIG. 4 illustrates a side view of an exemplary bandage-style
sensor with multiple removable ring structures applied to a
patient's finger;
[0023] FIG. 5 illustrates a perspective view of an exemplary
bandage-style sensor with an adjustable-diameter ring structure
with a hinge applied to a patient's finger;
[0024] FIG. 6 illustrates a top view of an exemplary embodiment of
a bandage-style sensor with alignment indicia to indicate placement
for a ring structure;
[0025] FIG. 7A illustrates a perspective view of an exemplary
embodiment of a bandage-style sensor with an oval annular structure
that contacts the sensor at the sides of the finger;
[0026] FIG. 7B illustrates a cross-sectional view of the sensor and
oval annular structure of FIG. 7A;
[0027] FIG. 8 illustrates a side view of an exemplary embodiment of
a Y-style sensor with an annular structure;
[0028] FIG. 9 illustrates a side view of an exemplary embodiment of
a bandage-style sensor with an annular structure including a
collar;
[0029] FIG. 10 illustrates a perspective view of an exemplary
embodiment of a bandage-style sensor with an arched semi-annular
structure;
[0030] FIG. 11 illustrates a perspective view of a kit including a
bandage-style sensor and multiple ring structures of different
diameters and widths; and
[0031] FIG. 12 illustrates a pulse oximetry system coupled to a
multi-parameter patient monitor and a sensor according to
embodiments of the present invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0032] One or more specific embodiments of the present invention
will be described below. In an effort to provide a concise
description of these embodiments, not all features of an actual
implementation are described in the specification. It should be
appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0033] In accordance with the present technique, sensors for pulse
oximetry or other applications utilizing spectrophotometry are
provided that reduce signal artifacts by reducing sensor
deformation in response to movement. For example, sensors are
provided that have various removable rigid annular structures
adapted to reduce the effect of motion or outside forces on sensor
measurements by deflecting such forces away from the sensing
components and/or preventing movement of the sensing components
relative to one another. Such rigid annular structures provide
multiple advantages. For example, they are relatively inexpensive,
are easy to apply to a patient, and may be made in multiple sizes
to accommodate differences in patient anatomy.
[0034] Signal artifacts in pulse oximetry are often generated by
the movement of the pulse oximetry sensor relative to the optically
probed tissue, which is typically caused by patient movement.
Because pulse oximetry is often used in settings where it is
difficult to prevent patient motion, it is desirable to provide a
mechanism for reducing the effects of motion on the pulse oximetry
measurement. Generally, sensors are vulnerable to motion artifacts
when the optical distance between a sensor's emitter and detector
varies due to an undesired mechanical change in the conformation of
the sensor while in use.
[0035] A change in optical distance may include any change in
position or geometry of the emitter and/or the detector relative to
the tissue or relative to each other. More specifically, a change
in optical distance may involve a change in the path length, a
change in the angle of the emitter or detector relative to one
another, and/or a change in the angle of the emitter or detector
relative to the tissue. For example, signal artifacts may be caused
by moving a sensor in relation to the tissue, by increasing or
decreasing the physical distance between emitters and detectors in
a sensor, by changing the direction of emitters or detectors with
respect to tissue or each other, by changing the angles of
incidence and interfaces probed by the light, by directing the
optical path through different amounts or types of tissue, or by
expanding, compressing or otherwise altering tissue near a sensor.
A tapping or pressing motion by a patient may serve to compress a
flexible bandage sensor, decreasing the path length between the
emitter and detector. A jerking or flexing motion may separate the
emitter and detector, thus increasing the optical path length.
Additionally, any of the above motions may twist or bend the
sensor, causing the angle of the emitter and/or the detector to
change relative to the sensor and each other. As sensors do not
typically emit nor detect light omnidirectionally, any motions that
lead to variations in angle of sensor components may alter the
amount of light detected, and may force detected light through
different portions of tissue. In any case, variability in the
optical path length due to motion can cause motion artifacts and
obscure the desired pulse oximetry signal. Thus, it is desirable to
reduce the effects of patient movement and outside forces on a
sensor's emitter and detector such that their movement relative to
one another is reduced.
[0036] By deflecting forces away from the sensing components such
that the effective force experienced by the sensing components may
be mitigated, the sensors provided herein limit the modulations of
detected light that may occur and the resulting measurement errors.
These sensors substantially reduce the occurrence of motion
artifacts by minimizing the effects of outside forces or patient
motion on the sensing components of the sensor.
[0037] Sensors are disclosed herein having removable rigid
structures to reduce the effect of motion or outside forces on the
measurements of physiological parameters, such as pulse oximetry
measurements. Such rigid structures are generally annular, and may
include structures that are partially annular, e.g. unclosed
semicircular or partial ring structures. The rigid annular
structures may be adapted for use on any patient digit, or may be
adapted to be used on any other patient tissue, such as a foot,
hand, or wrist, that may accommodate an annular structure.
[0038] The rigid annular structures may be formed from plastic,
polymeric material, metal, wood, composites or any other suitable
rigid material. For example, the annular structures may generally
hold their shape with forces equal to or greater than 100 grams. In
certain embodiments, it may be advantageous to provide lightweight,
disposable rigid annular structures for use with disposable
bandage-type sensors. In other embodiments, the rigid annular
structures may be reusable. In such an embodiment, it may be
advantageous to provide rigid annular structures that may be easily
cleaned. In specific embodiments, the rigid annular structures may
include additional non-rigid motion damping components, such as one
or more spring or a foam layer, in order to enhance their
motion-deflecting properties.
[0039] FIG. 1 illustrates an exemplary bandage-type sensor 10A
applied to a patient's digit 13. The sensor 10A has a removable
ring 14 disposed on the sensor body 12. The sensor 10A is adapted
to be placed onto the patient digit 13, and may be further secured
by a bandage or adhesive. The removable ring 14 is a rigid annular
structure that may deflect a force that may otherwise result in an
emitter 16 and detector 18 moving relative to one another. When a
patient scratches or taps using the digit 13, the removable ring 14
deflects the force of the motion by spreading the force equally
around the removable ring 14, which results in a reduction of the
effects of the motion on the emitter 16 and the detector 18. The
removable ring 14 may be of any suitable diameter to provide a fit
for the patient's digit 13. Further, the removable ring may be of
any suitable width. A ring may be only so wide as to cover 10% or
less of the exterior (i.e. not in contact with the tissue when
applied) surface area of the sensor body 12 when applied. In
alternate embodiments, it may be advantageous for the ring to be
wider, and to cover greater than 20%, greater than 30%, or greater
than 50% of the exterior surface area of the sensor body 12 when
applied. Wider rings may deflect forces over a broader area of the
sensor.
[0040] FIG. 2 illustrates an alternative embodiment of a sensor 10B
in which the rigid annular structure is a removable thimble 20 that
may be applied to a sensor body 12 in order to mechanically
stabilize the emitter 16 and the detector 18 after application of
the sensor 10B. The thimble 20 may be slid over the fingertip after
the sensor body 12 has been applied to the digit. The thimble 20
may be generally useful for deflecting motion caused by tapping
with the fingertip.
[0041] FIG. 3 illustrates an alternate embodiment of a sensor 10C
in which the rigid annular structure is a sleeve 22 that may be
applied to a sensor body 12 in order to mechanically stabilize the
distance between the emitter 16 and detector 18 after application
of the sensor 10C. The sleeve 22 may be removably applied to a
digit after the sensor body 12 is in place. The sleeve 22 may, in
certain embodiments, cover a finger joint to prevent bending or
flexing. In such an embodiment, the removable sleeve 22 may provide
the further advantage of adding rigidity to a relatively flexible
bandage-style sensor without adding the cost associated with
reusable clip-style sensors.
[0042] In certain embodiments, it may be advantageous to apply
several annular structures to a sensor body in order to deflect
mechanical forces at different locations. FIG. 4 illustrates an
embodiment of a sensor 10D in which rings 14a, 14b, and 14c have
been applied to the sensor body 12. The ring 14c has been placed
directly over the area of the sensor body 12 that includes the
emitter 16 and the detector 18. Rings 14a and 14b are placed over
areas of the sensor body 12 closer to the joint of the digit 13.
Such an arrangement provides the opportunity to minimize forces
acting over a wide portion of the sensor body 12 while maintaining
a relatively lightweight and flexible sensor structure. In an
alternative embodiment (not shown), the rings 14 may be connected
to one another by one or more elongated strips to provide
additional stability to the sensor assembly while maintaining a
relatively lightweight structure. In other embodiments, such
elongated strips may provide the advantage of holding the rings in
position relative to one another, and may be rigid or relatively
flexible to allow the finger to flex or bend slightly.
[0043] In order to achieve a more conforming fit for an annular
structure as provided herein, it may be advantageous to provide
sensors that include annular structures with adjustable diameters,
as shown in FIG. 5. A sensor 10E has an adjustable ring 24 placed
on the sensor body 12. The adjustable ring 24 may open at a hinge
26 and may be adjusted with a strap 28. The adjustable ring 24 may
be sized to fit over a fingertip section of the patient's digit 13,
which may include the emitter 16 and the detector 18, or may be
adjusted to fit over the relatively broader joint section of the
patient's digit 13.
[0044] As shown in FIG. 6, bandage-style sensors as provided herein
may include alignment indices to indicate the proper placement of
an annular structure on the sensor body. A sensor 10F is shown with
alignment indices 30 that provide an indication of proper placement
of a ring or other annular structure on the sensor body 12. In
order to reduce the effects of motion on a sensor signal, it is
advantageous to prevent such motion from disturbing the position of
the emitter 16 and the detector 18 relative to one another. Thus,
in certain embodiments, the alignments indices may indicate
placement of an annular structure over a portion of the sensor body
12 that includes the emitter 16 and the detector 18.
[0045] In certain embodiments, it may be advantageous to provide an
annular structure that does not closely conform to the digit. For
example, a sensor 10G with an annular structure 52 shown in FIG. 7A
and FIG. 7B only touches the digit 13 in certain areas. The sensor
10G includes an oval annular structure 52 that is adapted to be
placed on the digit 13 over a sensor body 12. The annular structure
52 conforms closely to the sides of the digit 13, but does not
touch the top or bottom of the digit 13. The annular structure 52
may include alignment indices 54 indicating the portions of the
annular structure 52 corresponding to sides of the digit. Thus, a
patient or healthcare worker is alerted to the proper placement of
the annular structure on the sensor body 12. Such an arrangement of
the annular structure 52 over the sensor body 12 tends to spread
forces away from the emitter 16 and the detector 18. For example,
if the digit 13 engages in a downward tapping motion, the annular
structure 52 spreads the force of the motion around its structure.
As the annular structure 52 only touches the digit 13 on the sides
of the digit 13, the impact of the downward tapping force, shown by
arrows 53 in FIG. 7B, is concentrated on the sides of digit 13, and
thus the impact is generally directed away from the emitter 16 and
the detector 18.
[0046] As shown in FIG. 8, annular structures as provided herein
may be used with any appropriate sensor, including Y-style sensors
or other cable sensors. As depicted, a sensor 10H includes a
flexible Y-style cable 56 with an emitter 16 and a detector 18. An
annular structure 58 may be slid over the Y-style cable 56 after it
has been placed on the digit 13. The annular structure 58 not only
serves to deflect forces away from the emitter 16 and the detector
18, but may also help hold the Y-style cable 56 in place.
[0047] FIG. 9 shows an alternate embodiment of a sensor 10I with a
collar structure 60 that is generally in the shape of an
Elizabethan-style collar that substantially encircles the fingertip
region. The collar structure may be slid over the sensor body 12
and acts as a guard to prevent motion of the digit 13. A patient
wearing such a sensor 10I may momentarily forget the presence of
the sensor 10I and attempt to scratch or otherwise move the digit
13. The presence of the collar structure 60 may prevent the patient
from being able to vigorously move the digit 13.
[0048] FIG. 10 shows an alternate embodiment of a sensor 10J that
includes an arch structure 61 with protruding prongs 62. The arch
structure 61 may be placed over the digit such that the protruding
prongs extend in the direction most likely to experience outside
forces. For example, during surgery, a patient may be positioned
with the palm of the hand facing up. In such an embodiment, the
arch structure 61 may be placed over the sensor body 12 such that
the protruding prongs 62 are directed away from the palm and
towards an operating table or other surface. Alternatively, an
active patient may place the arch structure 61 such that the
protruding prongs 62 face towards the palm to absorb forces from
scratching or tapping. In the event of a downward tapping motion,
the prongs 62 may deflect the motion of tapping, spreading much of
the impact through the arch structure 61 and away from the emitter
16 and the detector 18. The protruding prongs 62 may be rigid, or
may include motion damping structures such as springs (not
shown).
[0049] FIG. 11 shows a kit 32 that includes a sensor body 12 and
multiple rings 34, 46, 48, and 50. It should be understood that the
depicted embodiment of a kit 32 including is merely exemplary, and
a kit 32 may include any suitable number of rings 34, 46, 48, and
50 or any other rigid annular structure as provided herein. In one
embodiment, the rings 34, 46, 48, and 50 may be of a variety of
sizes, which may include a variety of diameters, profiles, and/or
widths. In certain embodiments, a kit 32 may include a subsection
of sizes that generally correspond to sizes appropriate for a
certain type of patient, such as an adult or a child. In one
embodiment, the rings 34, 46, 48, and 50 may have different
diameters that are sized to correspond with standard jewelry sizes
of rings. A healthcare provider or patient may select the
appropriately sized ring to apply to the sensor body 12. For
example, an individual ring 34 (such as 34a) may be selected from a
group having different diameters for having the characteristics of
providing a conforming, but not overly tight, fit over the portion
of the sensor body 12 that contains the emitter 16 and the detector
18. In other embodiments, a ring may be wider, such as the range of
widths shown in rings 34a, 34b, 34c, and 34d. In certain
embodiments, it may be advantageous to select a wider ring 34d or
50d (depending on the ring diameter needed) that covers a greater
percentage of the sensor body 12 when the patient is
non-ambulatory, as a wider ring 34d may mitigate forces along more
of the sensor body 12. However, an ambulatory patient may prefer a
narrower ring such as 34a or 50a that does not prevent flexing of
the finger joint. In another embodiment (not shown), the kit 32 may
include rings of a variety of different colors and/or decorative
patterns. Such an embodiment may provide enjoyment for a young
patient, who may be allowed to select a ring of a preferred color
or pattern. Additionally, colored and/or patterned rings may be
used in a nursery to identify infants by gender or other clinical
characteristics.
[0050] A sensor, illustrated generically as a sensor 10, may be
used in conjunction with a pulse oximetry monitor 36, as
illustrated in FIG. 12. It should be appreciated that the cable 38
of the sensor 10 may be coupled to the monitor 36 or it may be
coupled to a transmission device (not shown) to facilitate wireless
transmission between the sensor 10 and the monitor 36. The monitor
36 may be any suitable pulse oximeter, such as those available from
Nellcor Puritan Bennett Inc. Furthermore, to upgrade conventional
pulse oximetry provided by the monitor 36 to provide additional
functions, the monitor 36 may be coupled to a multi-parameter
patient monitor 40 via a cable 42 connected to a sensor input port
or via a cable 44 connected to a digital communication port.
[0051] The sensor 10 includes an emitter 16 and a detector 18 that
may be of any suitable type. For example, the emitter 16 may be one
or more light emitting diodes adapted to transmit one or more
wavelengths of light in the red to infrared range, and the detector
18 may one or more photodetectors selected to receive light in the
range or ranges emitted from the emitter 16. Alternatively, an
emitter 16 may also be a laser diode or a vertical cavity surface
emitting laser (VCSEL). An emitter 16 and detector 18 may also
include optical fiber sensing elements. An emitter 16 may include a
broadband or "white light" source, in which case the detector could
include any of a variety of elements for selecting specific
wavelengths, such as reflective or refractive elements or
interferometers. These kinds of emitters and/or detectors would
typically be coupled to the rigid or rigidified sensor via fiber
optics. Alternatively, a sensor 10 may sense light detected from
the tissue at a different wavelength from the light emitted into
the tissue. Such sensors may be adapted to sense fluorescence,
phosphorescence, Raman scattering, Rayleigh scattering and
multi-photon events or photoacoustic effects. For pulse oximetry
applications using either transmission or reflectance type sensors
the oxygen saturation of the patient's arterial blood may be
determined using two or more wavelengths of light, most commonly
red and near infrared wavelengths. Similarly, in other
applications, a tissue water fraction (or other tissue constituent
related metric) or a concentration of one or more biochemical
components in an aqueous environment may be measured using two or
more wavelengths of light. In certain embodiments, these
wavelengths may be infrared wavelengths between about 1,000 nm to
about 2,500 nm. It should be understood that, as used herein, the
term "light" may refer to one or more of ultrasound, radio,
microwave, millimeter wave, infrared, visible, ultraviolet, gamma
ray or X-ray electromagnetic radiation, and may also include any
wavelength within the radio, microwave, infrared, visible,
ultraviolet, or X-ray spectra, and that any suitable wavelength of
light may be appropriate for use with the present techniques.
[0052] The emitter 16 and the detector 18 may be disposed on a
sensor body 12, which may be made of any suitable material, such as
plastic, foam, woven material, or paper. Alternatively, the emitter
16 and the detector 18 may be remotely located and optically
coupled to the sensor 10 using optical fibers. In the depicted
embodiments, the sensor 10 is coupled to a cable 38 that is
responsible for transmitting electrical and/or optical signals to
and from the emitter 16 and detector 18 of the sensor 10. The cable
38 may be permanently coupled to the sensor 10, or it may be
removably coupled to the sensor 10--the latter alternative being
more useful and cost efficient in situations where the sensor 10 is
disposable.
[0053] The sensor 10 may be a "transmission type" sensor.
Transmission type sensors include an emitter 16 and detector 18
that are typically placed on opposing sides of the sensor site. If
the sensor site is a fingertip, for example, the sensor 10 is
positioned over the patient's fingertip such that the emitter 16
and detector 18 lie on either side of the patient's nail bed. In
other words, the sensor 10 is positioned so that the emitter 16 is
located on the patient's fingernail and the detector 18 is located
180.degree. opposite the emitter 16 on the patient's finger pad.
During operation, the emitter 16 shines one or more wavelengths of
light through the patient's fingertip and the light received by the
detector 18 is processed to determine various physiological
characteristics of the patient. In each of the embodiments
discussed herein, it should be understood that the locations of the
emitter 16 and the detector 18 may be exchanged. For example, the
detector 18 may be located at the top of the finger and the emitter
16 may be located underneath the finger. In either arrangement, the
sensor 10 will perform in substantially the same manner.
[0054] Reflectance type sensors also operate by emitting light into
the tissue and detecting the light that is transmitted and
scattered by the tissue. However, reflectance type sensors include
an emitter 16 and detector 18 that are typically placed on the same
side of the sensor site. For example, a reflectance type sensor may
be placed on a patient's fingertip or foot such that the emitter 16
and detector 18 lie side-by-side. Reflectance type sensors detect
light photons that are scattered back to the detector 18. A sensor
10 may also be a "transflectance" sensor, such as a sensor that may
subtend a portion of a baby's heel.
[0055] While the invention may be susceptible to various
modifications and alternative forms, specific embodiments have been
shown by way of example in the drawings and have been described in
detail herein. However, it should be understood that the invention
is not intended to be limited to the particular forms disclosed.
Indeed, the present techniques may not only be applied to
measurements of blood oxygen saturation, but these techniques may
also be utilized for the measurement and/or analysis of other blood
and/or tissue constituents. For example, using the same, different,
or additional wavelengths, the present techniques may be utilized
for the measurement and/or analysis of carboxyhemoglobin,
methemoglobin, total hemoglobin, fractional hemoglobin,
intravascular dyes, and/or water content. Rather, the invention is
to cover all modifications, equivalents, and alternatives falling
within the spirit and scope of the invention as defined by the
following appended claims.
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